The overall goal of this proposal is to identify differences in patterns of electrically-elicited perceptions across sites of stimulation with the aim of optimizing the perception of temporal information by cochlear implant (Cl) users. Modern CIs have an array of electrodes that provide electrical stimulation at multiple sites in the cochlea. The neural activity generated by this electrical stimulation is tonotopically distributed which allows the creation of a defined map where spectral information is allocated to specific locations or channels and specific temporal information is delivered to each location. However, it has been shown that subjects do not effectively use all of the available sites and that their overall performance is widely variable. It is hypothesized that channel interaction and differences in the uniformity of neural survival might be some of the physiological factors that underlie the variability in temporal acuity reported across listeners and across sites of stimulation. As a first step, the proposed study aims at identifying these differences using measures of temporal modulation detection threshold (MDT). Previous studies have shown a strong correlation between speech recognition and subjects'overall temporal processing capabilities using MDT measure in quiet. However, temporal cues become more salient in situations that require listeners to stream or segregate conflicting auditory information. Hence a cross-examination between speech recognition and masked MDTs would offer a more realistic methodology to evaluate temporal processing in Cl users in order to develop new approaches to optimize these processes. To date, this area has not been examined and it will be the focus of this research application. To accomplish this goal the following specific aims will be pursued: 1) to examine patterns and relation of MDTs with and without interleaved maskers across sites of stimulation;2) to determine whether speech recognition for consonants, vowels, and sentences can be improved by selecting sites with lowest MDTs;data obtained in specific aim 1 will be used to remap subjects'speech processor using two approaches that allow comparisons of performance on maps with the best masked MDT sites and maps with worst masked MDT sites;and 3) to examine the relation between across-site means and across-site variances of MDTs (masked and non-masked) and speech recognition for consonants, vowels, and sentences. Results from this work will further our understanding of temporal processing capabilities in Cl users and have significant implications for programming speech processors and future clinical practice.